Jet Stream - A strong high level wind found in the atmosphere that can reach speeds in excess of 200 mph, usually occurring 6 to 9 miles above the ground. These winds often steer the movement of surface air masses and weather systems.

La NiÃ±a - A widespread cooling of the surface waters of the eastern tropical Pacific Ocean. Itâ€™s the opposite of El NiÃ±o.

Lake Effect Snow - Localized snow that forms on the downwind side of large lakes. Itâ€™s common in the late fall and winter in the Great Lakes region when cold, dry air picks up moisture from the unfrozen lake surfaces.

Latitude - The position of the earthâ€™s surface north or south of the equator.

Leeward Side - The side of an object that is facing away from the direction that the wind is blowing.

Lightning - An enormous and very hot spark of electricity produced by thunderstorms. The lightning bolt itself can heat the air through which it travels to 54,000Â° F.

Longitude - The position of the Earthâ€™s surface east or west of the Greenwich meridian.

Low Pressure System - A whirling mass of warm, moist air that generally brings stormy weather with strong winds. When viewed from above, winds spiral into a low-pressure center in a counterclockwise rotation in the Northern Hemisphere.

Macroburst - A large downdraft of air with an outflow diameter of 2.5 miles or greater and damaging winds lasting from 5 to 20 minutes. This may reach tornado intensity.

Microburst - A small downdraft of air with an outflow diameter of less than 2.5 miles with the peak winds lasting from 2 to 5 minutes. This can effect a planeâ€™s performance.

Meridional Flow - Itâ€™s when the winds in the upper levels of the atmosphere blow from a North to South component which usually creates a buckling effect in the jet stream.

Meteor - Itâ€™s a shooting star. The brief streak of light as an object from space plunges into the Earth's atmosphere.

Meteor Shower - An event when hundreds of meteors or shooting stars appear in the sky at a specific time.

Meteorite - It's a meteor that reaches the Earth's surface.

Meteorologist - A scientist who studies and predicts the weather. Meteorologists use sophisticated equipment, like Doppler radar and supercomputers, but they also rely on old-fashioned sky watching.

Meteorology - The study of the atmosphere and all its phenomena, including weather and how to forecast it.

Mist - Water droplets so small that they are floating in the air. Because mist droplets do not fall, mist is a type of fog.

Monsoon - A seasonal wind, found especially in Asia that reverses direction between summer and winter and often brings heavy rains.